The long range purpose of this project is to study lysogenic (especially lysogenic conversion) means of genetic exchange (transduction, transformation) in Group A streptococci. A high percentage (99 percent) of lysogeny was found. We are now investigating the characteristics, and possible changes therein, of streptococcal cells before and after the acquisition of a prophage. The characteristics studied are: (1) serological variability, (2) colonial morphology, (3) production of hemolysins and erythrogenic toxin, (4) ability to transform, and (5) ability to become a transducing donor or recipient.